Method and apparatus for exposing photosensitive material



April 28, 1964 METHOD AND APPARATUS FOR EXPOSING PHOTOSENSITIVE MATERIAL VACUUM SYSTEM 5. BERTRAM ETAL 3,131,020

Filed Sept. 20, 1962 .S/DNE) L. HAS/N .S/DA/Ey BERT/2AM lNl/ENTORS A 77'0/2NEY United States Patent M 3 131 020 METHOD AND APfiARkTUs FOR EXPOSING PHOTOSENSITIVE MATERIAL Sidney Bertram and Sidney L. Hasin, Los Angeles, Calif.,

This invention relates to a method and apparatus for exposing photosensitive materials and more particularly to'the utilization of cathode ray tube beam writing apparatus and techniques for electronically prescribing and.

exposing selected areas on the material.

There is a need for improvement in techniques for the rapid exposure and development of photosensitive materials. One example of this may be found in traffic control centers, military command posts, stock inventory and control centers and in area surveillance systems where information bearing alphanumerics, symbols and lines are made on film frames or chips which are projected onto a display. Such displays are viewed by observers who make decisions based upon the latest available informa tion. For this reason the display must be continually updated with the latest information as soon as possible after it becomes available.

In one application an ultraviolet sensitive film is ex: posed through an appropriate information bearing mask whereby a beam of light is moved over the film to draw a desired configuration thereon. This type of film may be easily developed with dry processing techniques and therefore is very convenient to use. Such film is of relatively slow speed, is insensitive to ordinary light, and hence may be easily handled. However, the film requires exposure to high intensity light and the presently known methods of exposure through a mask or by drawing a desired configuration on the film with a beam of'light makes the exposure process relatively slow and not readily adaptable to the processing of high density incoming electronic data.

It is therefore an object of this invention to provide a method and apparatus for translating electronically represented information into a light pattern and for easily and rapidly exposing a film therewith.

It is well known that radiation from the phosphor on the inside face of a cathode ray tube may be used to expose film chips placed adjacent the face of the tube. However, in order to expose certain films of, relatively slow speed with radiation from. the very short persistence phosphors presently used in cathode ray tubes, a high beamdensity on the order of ten times that normally permissible with present day phosphors is required. If the film is exposed by means of a spot that is relatively stationary on the face of the cathode ray tube, evenfor a short period of time, the phosphor is likely to be burned at the point of impingement of the electron beam, rendering the tube useless.

. In view of this, a feature of therpresent invention provides means for sufiiciently exposing the film by means of a cathode ray tube without allowing the electron beam to burn the phosphor on the face of the tube.

Briefly, the invention is based on the recognition that when two objects are moving relative to a third object, the movements of the two objects may be so controlled that the two objects are not moving relative to each other, or may be caused to move relative to each other in a coordinated predetermined manner. In carrying out this principle, the beam of a cathode ray tube is caused to move over the face of the tube. The film to be exposed is positioned in close proximity to the tube face and is moved in synchronism with thefmovement of the beam and by a corresponding amount, thereby insuring 3,131,020 Patented Apr. 28, 1964* adequate exposure of the film at a desired position thereon without danger of burning the phosphor on the tube: This stop motion technique permits the film to receive illumination over a sufficiently long period to properly expose the film, yet the electron beam used in the film exposure process does not burn the phosphor. With the film and the beam moving in controlled syn-1 chronization relative to the face of the tube, the beam additionally may bemoved relative to the film in response to information writing signals. This results in exposing the film in the desired manner and the film exposure is unaffected by the synchronized film and beam movement. a The invention will be better understood from the following description, tak'enin conjunction with the accompanying drawing, which is a perspective view with parts broken away, showing one embodiment of the invention wherein beam movement is synchronized with film movement.

Referring now to the drawing, there is shown a conventional cathode ray tube 10 having X and Y deflection plates 12, '14. An electron gun 16 provides an electron beam which impinges on the phosphor-coated face or target 18 of the tube and'causes the phosphor to emit radiation, which may be in the form of ultraviolet light, at the point of impingement. The phosphor 20 is preferably of a very short persistence type, such as thatcommonly known as P16, which is often used in flying spot scanning apparatus. It has a persistence of the order of a microsecond or less and upon excitation emits a radiation rich in ultraviolet wavelength energy. To prevent optical dispersion through the tube face, the face preferably contains optical fibers 22 which extend from the inner to the outer surfaces of the face to provide for greater effective resolution for contact exposure.

A photosensitive film chip 24 is mounted on a fiat, sintered metal base plate 26 which is located about two mils from the optically ground flat exterior of the fiber optics face 18 of tube 10. This photosensitive film chip maybe of the type that is sensitive to ultravioletlight, for example, and hence may be easily handled because it is insensitive to ordinary light. It thus may be exposed by the ultraviolet radiation from the phosphor of the tube. A vacuum hold-down system 28 secures the film chip 24 to the base plate 26 during the exposure operation andreadily releases the film at the completion ofits 'exposure, such as upon the turning of valve 30, for example, to release the vacuum. w

The base plate 26 has three precision bearings 32,34, 36, mounted in it,'each of which receives an eccentric element from an associated shaft, only shafts 38 and 40 and eccentric portions 38a and 49d being visible. One of these shafts such as the shaft 38, is rotated by a conventional motor system 42. Shafts 38, 40, and the third shift (not shown) whose ofi-center element fits within bearing 32, are rotatably mounted on a frame 44 which is positioned in front of tube 10. v j v The ofl-center'element'iisa' of shaft 38 fits within bearing 34 and upon'rotation of the shaft'38 movement is imparted to the plate 26 in directions substantially transverse to the tube axis and substantially parallel to the face 18 of the tube. The other two shafts have similaroif-center elements which follow the movement of the plate and stabilize the plate causing it to hold its initial orientation while it translates arounda circle of a diameter determined by the degree of eccentricity of the olfcenter elements from their axes of rotation.

The diameter of the circular path followed by a point on the plate may be arbitrary, mils being exemplary, but'in accordance with the present invention preferably exceeds the height of any symbols being written by the beam to insure continuous beam movement over 'the tube face during the exposure time. Since the electron beam in the tube 10 is to follow the movement of the film chip 24 to avoid relative movement therebetween, the speed of rotation of the base must be such as to keep the beam from dwelling in one position on the tube suflicient- 1y long to' burn the phosphor. The speed also must be slow enough to excitethe phosphor properly. A speed of one cycle per second for a 100 mil diameter circle has been found to be adequate for this purpose using one type of film.

The movement of base plate 26 may be utilized to control movement of the electron beam of tube 10 so as to be in synchronization therewith. A resolver 46 of conventional design (such as is obtainable from Bendix Corporation or Kearfott Division, General Precision Inc.) is suitably coupled to one of the driven shafts, such as the shaft 40, and provides an indication of the instantaneous position of the plate 26 in its path of motion. This resolver produces voltages proportional to the sine and cosine of the angle of rotation of the shaft 40. The output signals from sine and cosine terminals 48, 50, of the resolver are applied to deflection amplifiers 52, 54 of the cathode ray tube. These amplifiers are of the operational amplifier type that can be used to sum any number of diflerent voltages.

As is well known, if sine and cosine functions of the same angle having equal amplitudes are respectively placed on the horizontal and vertical deflection plates of a cathode ray tube, the resulting beam pattern will be a circle. By adjusting the amplitude of the functions, the diameter of the circle may be varied. Thus, in the present case, the outputs of the deflection amplifiers 52 and 54 are connected to the deflection plates 12 and 14, respectively, of the tube 10 to cause its electron beam to trace a circle on the face of the tube in synchronism with the movement of the plate and film chip. Certain proportionality constants are adjusted, i.e. gear ratios, resolver efiiciency, amplification factors, etc., such that the spot will remain stationary with respect to the moving plate 26 on which the film chip 24 is mounted. These adjustments may be made easily by one skilled in the art, so that a single spot on the film will be exposed by the phosphor spot as they both travel in a circular orbit.

Voltages that deflect the electron beam in accordance with information to be recorded are provided by an information writing system 56. In one arrangement, the information Writing system 56 may include computercontrolled digital registers and a digital-to-analog converter for supplying voltages (gross position voltages) to deflect the electron beam to a desired position for recording information on the film. In the present application these positioning voltages have superimposed on them the voltages derived from the resolver 46, as previously explained, to cause the spot to move around a circular path upon the phosphor while at all times remaining stationary with respect to and/or in registration with a desired point on the moving film.

The information writing system may also include means for generating symbols, such for example, as a device available commercially from CBS Laboratories, Stanford, Connecticut and known under the trade name Vidiac. This symbol generator provides voltages, which when amplified by the amplifiers 52 and 54, deflect the electron beam to define symbols on the face of the cathode ray tube. The symbol generator also provides intensity control signals, which are amplified by an amplifier 58 and then connected to an intensity grid in the cathode ray tube 10.

After the film chips have been exposed in the manner described, they may be dry processed and be ready for projection within seconds from the time the information is written onto the chips from the electron beam.

Although the invention has been described with reference to the exposing of ultraviolet sensitive film, it is understood that the invention is not limited to the use of any particular type or types of film or other photosensitive material nor to any particular configuration of apparatus for producing a radiation emitting spot in response to a deflected beam acting upon a sensitive target such as a cathode ray tube. It is moreover apparent that the rela- 5 tive movement contemplated by the present invention between the photosensitive material and target although preferably circular in nature need not be limited thereto.

Having thus described a preferred embodiment of the present invention, it is apparent that many improvements and modifications will readily occur to those skilled in the art. It is therefore to be understood that the scope of this invention is not limited to the embodiment illustrated but is to be defined by a just interpretation of the appended claims.

What is claimed is:

1. Apparatus for exposing photosensitive material comprising:'

a radiation-emitting spot producing means including a target responsive to a deflectable beam incident upon said target;

means for movably positioning photosensitive material responsive to the radiation emitted by said spot adjacent said target for exposure thereby;

means for moving said material relative to said target;

and

means for deflecting said beam in accordance with the movement of said material to expose but one specific area on said material to the radiation emitted by said spot.

2. Apparatus for exposing photosensitive material comprising:

a radiation-emitting spot producing means including a target responsive to a defleotable beam incident upon said target;

means for movably positioning photosensitive material responsive to the radiation emitted by said spot adjacent said target for exposure thereby;

means for moving said material relative to said target;

first means for deflecting said beam in accordance with the movement of said material to expose but one specific area on said material to the radiation emitted by said spot; and

second means acting during the operation of said first means for deflecting said beam in accordance with image information to expose other specific areas on said material for delineating prescribed images there- 3. Apparatus for exposing photosensitive material comprising:

a cathode ray tube having a face an an electron beam for providing a movable, radiation-emitting spot on said face;

means for mounting the photosensitive material for exposure by said spot;

means for moving said material in a direction substanstantially parallel to said face; and

means responsive to movement of said material for deflecting said electron beam in synchronism therewith to prevent relative movement between said spot and said material.

4. Apparatus for exposing photosensitive material comprising:

a cathode ray tube having a face and an electron beam for providing a movable, radiation-emitting spot on said face;

means for mounting the photosensitive material for exposure by said spot;

70 means for moving said material to cause a point on said material to move in a circle; and

means responsive to movement of said material for deflecting said electron beam in synchronism therewith to prevent relative movement between said spot and said material.

5. Apparatus for exposing photosensitive material comprising:

a cathode ray tube having a face with a very short persistence phosphor coating and an electron beam for providing a movable, radiation-emitting spot on said face;

means for mounting the photosensitive material for exposure by said spot;

means for deflecting said electron beam to move said spot in accordance with signals representing information to be placed on said material, and

means for superimposing a second motion on said spot to prevent burning of said phosphor, said last-mentioned means comprising means for moving said material; and

means responsive to movement of saidmaterial for deflecting said electron beam in synchronism therewith to prevent relative movement between said spot and said material due to movement of said material.

6. Apparatus for exposing photosensitive material comprising:

holding means for holding the material to be exposed;

a cathode ray tube having an axis, a face and an electron beam for providing a radiation-emitting spot on said face;

an information writing system for providing signals for causing deflection of the electron beam and movement of the spot in a preselected manner, and

means for moving the spot and material in a coordinated manner and including means for moving said holding means in a direction substantially transverse to the tube axis and substantially parallel to the face of the tube;

position sensitive means for converting the movement of said holding means into signals indicative of the position of the holding means, and

means responsive to the signals from the position sensitive means and the signals from the information Writing system to cause movement of the spot on the face of the tube to prevent relative movement between the spot and the material except for relative movement caused by signals from said information writing system.

7. Apparatus for exposing photosensitive material comprising:

a cathode ray tube having a phosphor-coated face and an electron beam for providing a movable, radiationemitting spot on said face;

means for mounting the photosensitive material for exposure by said spot; and

means for providing a plurality of types of signals for deflecting said electron beam to move and position said spot, said last-mentioned means comprising:

means for providing signals to position said spot on said face to record information on said material in a desired position,

means for providing signals to move said spot in accordance with information to be recorded on said material in said desired position, and

means for moving said spot on said face to prevent burning said phosphor and including means for moving said material; and

means responsive to movement of said material for providing signals for deflecting said electron beam in synchronism therewith to prevent relative movement between said spot and said material due to movement of said material.

8. Appanatus for exposing photosensitive material comprising:

a cathode ray tube having a phsophor-coated face and an electron beam for providing a movable, radiationemitting spot on said face;

means for mounting the photosensitive material adjacent said face for exposure by said spot; and

means for providing three types of signals to deflect said electron beam to move and position said spot, said last-mentioned means comprising:

means for providing positioning signals to position said spot to record information on said material in a desired position,

means for providing signals to move said spot in accordance with information to be recorded on said material in said desired position, and

means for moving said spot on said face to prevent burning said phosphor and including means for moving said material to cause a point on said material to move in a circle lying on a plane substantially parallel to said face; and

means responsive to movement of said material for providing signals to cause said spot to move in a circle in synchronism with said material to prevent relative movement between said spot and said material due to movement of said material.

References Cited in the file of this patent UNITED STATES PATENTS Sabbah et al Sept. 24, 1935 Hunter Mar. 24, 1953 Wilner Apr. 7, 1959 

1. APPARATUS FOR EXPOSING PHOTOSENSITIVE MATERIAL COMPRISING: A RADIATION-EMITTING SPOT PRODUCING MEANS INCLUDING A TARGET RESPONSIVE TO A DEFLECTABLE BEAM INCIDENT UPON SAID TARGET; MEANS FOR MOVABLY POSITIONING PHOTOSENSITIVE MATERIAL RESPONSIVE TO THE RADIATION EMITTED BY SAID SPOT ADJACENT SAID TARGET FOR EXPOSURE THEREBY; MEANS FOR MOVING SAID MATERIAL RELATIVE TO SAID TARGET; AND MEANS FOR DEFLECTING SAID BEAM IN ACCORDANCE WITH THE MOVEMENT OF SAID MATERIAL TO EXPOSE BUT ONE SPECIFIC 